Lighter-than-air vehicles, such as aerostats, blimps, balloon, dirigibles, or airships, are used in many different applications, such as near large sporting, entertainment or cultural events, or in large metropolitan areas to provide advertising or to provide high level coverage of the events. Lighter-than-air vehicles are also used in high altitude applications, for the purpose of weather monitoring and/or military surveillance. In such instances, the higher a vehicle can operate translates into an increased amount of area that can be viewed for surveillance purposes and/or weather monitoring. Additionally, lighter-than-air vehicles that possess the ability to operate at altitudes above 50,000 feet, are not a hazard to commercial air traffic, are more difficult to detect and/or destroy, can be used for the surveillance of wide areas and thus provide a strategic and/or economic advantage.
Typically, high altitude lighter-than-air vehicles are made from laminates of materials that withstand a wide range of temperature variation, ozone degradation, exposure to ultraviolet radiation and daily expansion and contraction due to the wide temperature variations.
For example, U.S. Pat. No. 6,074,722 to Cuccias teaches a fabric laminate made of a layer of polyurethane resin that is used to bond layers of high strength liquid crystal thermotropic (melt spun) polyester (VECTRAN®), aromatic polyaramide (KEVLAR®), or polyester (DACRON®) fiber woven yarn to a polyvinyl fluoride (TEDLAR® or MYLAR®) layer, and having an outer layer of a material that is resistant to degradation by ultra violet radiation. This combination provides a laminate that is substantially imperious to helium or hydrogen gas and provides protection from degradation, wind erosion and the like.
U.S. Pat. No. 6,979,479 teaches a laminate of a liquid crystal polymer fiber yarn layer (VECTRAN®) as an interior surface, an adhesive layer, a polyimide layer, and a polyvinylidene fluoride (PVDF) layer which forms the exterior surface. The polyimide layer functions as a gas barrier for retaining helium or hydrogen. The polyvinylidene fluoride layer provides ozone and ultraviolet radiation protection.
For fabrics for lighter-than-air vehicles operating at high altitudes, it is also typical to have a thin metallic coating as one of the layers to reflect most of the incident solar radiation, reduce helium permeation, minimize the effects of lightning strikes, and provide a means for uniform static electric distribution over the hull surface.
Further, when the fabric panels or sections (e.g., hull sections) are assembled to form a lighter-than-air vehicle, platform or other inflated structure, while there is an effort to have the surface be as continuous as possible, there are instances where the fabric panels or sections (e.g., hull sections) are assembled in pieces and are joined edge-to-edge using structural seam tape. The structural seam tape is generally located on the inside surface or the surface facing the helium-containing portion of the lighter-than-air vehicle, platform or other inflated structure. A seam cover tape is generally located on the outside surface of the lighter-than-air vehicle, platform or other inflated structure, and is designed to protect and/or cover any gaps and/or seams located between one or more fabric panels or sections (e.g., hull sections).